Method and apparatus for power measurement and detection at ultrahigh frequencies



June 23, 1953 2,643,280

J. BERNIER METHOD AND APPARATUS FOR POWER MEASUREMENT AND DETECTION ATULTRAHIGH FREQUENCIES Filed Sept. 4, 1946 2 Sheets-Sheet l June 23, 1953BERNIER 2,643,280

METHOD AND APPARATUS FOR POWER MEASUREMENT AND DETECTION AT ULTRAHIGHFREQUENCIES Filed Sept. 4, 1946 2 Sheets-Sheet 2 h//aw//J aa/af W/sw05,4 /v 5 mv/5R,

f5 de; MLM@ A7'7 R/VEY Patented June 23, 1953 f l g 2,643,280

Y' METHOD'AND APPARATUS Fon` POWER c Y MEASUREMENT AND DETECTION ArULTRAHIGH 4retomar:oms

Jean Bernier, Paris, France, assigner to Compagnie Generale deTelegraphie Sans Fil, acorporation of France Application September 4,1946, Serial No. In France October 26, 1942 i section 1, Public Law 69o,August s, 1946 Patent expires October, 1962 -17 claims. (ci. 1v1-95)This invention relates to a new methodA and apparatus for powermeasurements and detection at ultra-high frequencies.

YOneof the objects of the present invention is to provide a method ofdetecting ultra-short elec- I tromagnetic waves limited' by a metallicsurface such as theinside surface of a cavity or of a dielectric guide.-V The principle of this method consists in pro- `viding the metallicsurf-ace limiting the waves t t ube detected with at least o'cne elementof a disrplaceable surface and detecting .the pressureof radiation,applied uponthe said element of surface by the wavesto' be detected.

Another object of the invention also concerns; devices` utilizing thesaid method, these devices, as w-attmeters and detectors ofA modulation,demonstrating a great sensitiveness 'and having no reaction upo-ntheload or tuning of thegenerator kthe invention, to measurements in acavity andv in a dielectric guide, respectively, will be understood fromthe following specification, in which: Y

' producing the waves to be detected.l The appli-'20 Acation ofthe-method of detection, accordingto Figure y1 diagrammaticallyillustrates a de- 25 tector embodying the principles of my invention;

Fig. 2 is a characteristic curve shewingthe resonance characteristicsofthe cavity 1n the detector illustrated in Fig. 1;

Fig. 3-diagrammaticallyillustrates my inven- 30 tion las applied to awattmeter;

Fig. 4 is a vector diagram'describmg the prlnf -ciplesfof my invention;v

Fig. 5 is a block diagram showing one manner of impressing highlfrequency waves upon a detector system operating in accordance. with myinvention; f l

Fig. 6'is a schematic view. of a pressure detector constructed inaccordance w1th my 1nvention; and

Fig. 7 is a cross sectional view of anapparatus carrying out theprinciples of my invention.

It is known that electromagnetic waves exert @on .a metallic surfacelimiting them, a` pressure of radiation which is normal to the surfaceand -which has at any time, by unity of surface, p

for value, taken in a positive direction to the normal, that is,comingfrom the interior towards I n Y f In this equation, holding good1n the case o the surface. perfectly conductive,E and are* quantitiesrepresented` at the considered point 'of the surface of theelectric andmagnetic fields measured in mixed Gauss C. G. S. units. A real pressuretakes place, orjasuction, according to the relative magnitudes of EandH.

In the case of a metallic surface enveloping the said waves, itisgenerally possible to determine the distribution of the electromagneticeld at the interior of the said surface and it results that from themeasureof the pressure of radiation on an elastic element therecan beinferred the strength of the high-frequency wave which reflects thereon.The measuring process accord- "ing to the invention, applied-toelectromagnetic waves of ultra-high frequency, is characterized by thefact that there'is measured, by means known in themselves-the pressurewhich they exert on at least one'felasticY element of high surfaceconductivity which,inserted in one of the metal wallson which-theyreflect, does not form any projection on this wall. First of alltherewill beconsidered the application of the invention, when utilizing aresonant cavity.' rIt is known lthat 'cavities are hollow,

metallic chambers, completely closed andv with -walls "of a highconductivity.- They have Adifferent methods of vibration, and,consequently, several natural wavelengths: these natural wave lengthsare of the same order of magnitude as their linear dimensions. Thus, aprismatic cavity-with a square base has a method of vibration(fundamental method) such that the nat- 'ural wave length is equal tothe length of the 'diagonal line of lthe base and is independentfromtheheight of the prism.

-'-'Ihesecavitieshave also a very high quality factorz'vfo'r a'cubehaving a wall of copper, of

20 cm.r eachside (natural wave length:v 28.3 cm.) thequality'factor isQ=33,000-in consequence it 0 is possible to sustain a considerableelectromagneticenergy in a cavity by means of a very'small exteriorcontribution.

` By applying the equation (1) mentioned above, to thegcase of aparallelepipedic case excited according to its fundamental method ofvibration, it is found that a pressure is exerted on the lateral wallsviz., according to the place considered, a

. pressure or a suction on the bases. At the center of the-bases theeffect is at its utmost and its means value in the course of time, is

llame-Tn *21p aryes where a (cms.) is the side of the square base Z(cms.) is the height of the parallelepiped p (watts) is the ultra highfrequency power of excitation.

For such a cavity, the natural wave length )(:a \/2 cm. (independentofthe height-l) this pressure is also expressed by:

On the bases of the parallelepiped, the zone of suction is centrallypositioned; it is approximately circular and of radius a \/2/4 or M4.

- .a .plate .of quartz.(or any other crystal) which is These results maybe qualitatively applied to all forms of cavity; they show, inparticular:

(l) That the pressure is rigorously proportional to the high frequencypower of excitation p;

(2) That the same is proportional the 3/2 power of the natural frequencyof the cavity.

(3) That, if the cavity is prismatic (or cylindrical) and excitedaccording to its fundamental method of vibration (natural frequencyindependent of height Z), .the less high the cavity,'the greater is thepressure.

I have set forth hereinafter a few numerical results which serve as avindication of the method of my invention.

There will be considered at first a cavity having a square base andwalls of copper, reso'nating on a wave length of cm., with a sideaff-'7.07 cm. and a height Iza/2:35 cm. The pressure of radiation is atits maximum in the centre of the base and has for value (suction)pmx=0.09 barye per watt of excitation.

This pressure can be detectedl through means known at the present time,such as microphones, piezoelectric quartz crystals,l etc.

The apparatus according to the invention is characterized by the factthat the elastic element of high surface conductivity on which it exertsthe pressure of radiationvcloselyts the form of the wall where it isinserted and connects with it by a joint o f such .dimensions that itshortcircuits for ultra-high frequency waves., I shall describehereinafter, by way of example, a form of the apparatus which enablesthe control of the quality of the modulation of the carrier Wave in aradioelectric station.

The detector is diagrammatically respresented in Fig. 1. It isessentially composed of a cavity C, the wall of which is pierced with ahole T. Close against this hole, at a very little distance of the wall,or else fixed at the wall, there is applied a disc or a metallicmembrane M (or simply, a metallized one) the role of which is onlyV totransmit the pressure of radiationto a microphonic relay R. This relay R(of a piezoelectric, electromagnetic or any other nature) is connectedto an ordinary telephone amplifier A, but having a first stageespecially Well designed;

Furthermore, in Fig. l there'is represented a loop and aA portion ofline L which permits of introducting'vinto the cavity the ultra highfrequency modulated power P. A means for adjusting the natural wavelength of the cavity (not shown in Fig. 1) must also-be. provided for.The usual means of tuningl are the `deformation of the wall of thecavity or .the deformation of the field within the cavity. The latterdeformation may, for example, be obtained with plunging rods. In thecase'of a prismatic cavity, it is metallized and inserted in the Wall ofthe cavity. The 'essential condition is that the part of the relay incontact with the field of the cavity should be metallic (or metallized)and of high superficial electric conductivity.

The device thus designed can be used for the detection of amplitudemodulation or for .the

frequency modulation of carrier waves of an ultra high frequency.

Actually, in the case of a carrier which is amplitude modulated, oneshall begin by so adjusting the cavity, that its natural frequency isyexactly equal to the frequency of the carrier. The

mechanical force acting upon relay, R. being rigorously proportional tothe high frequency power p brought into the device, the low frequencymodulation of. p will induce at the output of R. a low frequencycurrent, the magnitude of which will be rigorously proportional tovariable amplitude of p.

I provide another form of the apparatus as an embodiment of my inventionwhich permits the measuring directly of the power of oneV wave of ultraYhigh frequency pureor modied.

The resonance curve of a cavity being very acute, one may be lead for.the adjustment, to

couple. to the cavity of the detector an adequate load, so. as toyfiatten the resonance and thus increase the width of the frequency bandthat it is possible to detect without abnormal distortion.

I shall now describe, my way4 of example, another embodiment of theapparatus of my invention which enables, the direct measurement of thestrength of a pure or modulated ultra-high frequency Wave..

This instrument is diagrammatically represented in Figure 3. Itessentially comprises:

-(1) A cavity C. with highly conductive walls, into-which there isintroduced the power p to be measured through a coupling system L(preferably adjustable). This cavity is pierced with a hole T; y

V(2) VA disc or membrane M applied against the hole and designed fortransmitting the efforts due to :the electromagnetic field to a meter R.This disc may be either: fixed by the brims thereof fto Ythe wall of thecavity, or` (as it is shown in Fig. 3) located at a very little distancefrom the wall (a few V100 of a mm). The part of Ydisc M which is incontact with the electromagnetic field must be of a high superficialelectric conductivity;

(3) A dynamometer R permitting of measuring vthe effect transmitted byM. This dynamometer may be a micro-balance or any optical, electrical,magnetical, piezoelectrical, etc. system,` permitting of measuringforces of the order of magnitude of the dyne.

In Fig. 3, and by way of example, the dynamometer R is constituted by aplate of quartzof Curie cut, the extremities of which are one fixed atthe center` of discM and the other to a socket. The lateral faces of theplajte are metallized, which permitsof collecting the electric chargesappearing as al consequence of thev effortA trans- -mitted' by M. ThesechargesA are, measured. by

means of an electrometer (e. g., awireone) orfan electrometer valve It.'is 'known that the charges appearing on ythe quartz kowing-.to a fpiezoelectric effect are rigorously proportional to of the cavity inagreement with the -frequencyof In fcase-the'waves tobe measuredcirculate inthe power ytobe measured' by `means of.. an apl y propriatesystem (not represented inFig; 3);.

This tuning isshown, when reading-the electromf` eter by a displacementmaximum. Y

' (2) Adjustment of the coupling system L torhave a-'stationary Wave intheinlet feeder, which would cause the power introduced inthe cavityA tobe inferior to the power to be measured.

not

The exactitude of this adjustment is shown by n eter. p Then thedifference in the readings 'of theelectrometer with and Without ultrahigh frequency excitation ofthe wattmeter, multiplied: bythe anewmaximum inthe reading of the 'electromconstant of the instrument,gives thevalue` of the power of excitation V(a previous -calibration of.

the system of deformation of thecavity also gives the wave length).

'Ihe constant of the instrument depends on the constant of theelectrometer, of that of the quartz (all vconstantsv supposedly known)yand also of a constant relatedto the cavity. This latter, as thecalculations succintly developed at the -outset have shown, is connectedwith the quality factor of the cavity.

This coefficient is determined either by calculation, or experimentallyby plotting down, through the intermediary ofthe wattmeter, theresonance curve of the cavity. f

This vwattmeter, which permits fof measuring the power p introduced intothe cavity, .may also obviously operateas a detector when this power islow frequency modulated; the current circulating in the circuit ofthequartz is exactly propor- The following numerical examplewill show thesensitiveness of this wattmeter. Let us consider a parallelepipediccavity vhav,-

ing a square base, of a natural length of 10 cm.,'

already mentionedas an example. The membrane M is-supporsed to besquareand of side a/2; a force of 0.58 dyne per Watt of excitation is appliedupon this membrane. It is supposed, also,

that the plate of quartz used is 2 cm. long and 125* mm. thick; theconstant of the quartz will be:V f

(102e. s. U per .dyne

and it will appear on the armatures of the quartz a charge of 1.25. 1015 coulomb per watt `of ,eXcita-;

tion. And the electrometervalves aresensitive to charges 10 timessmaller. v

It is well understood that in the foregoing exe Vamples of detector orwattmeter, the A,choice of aA prismatic cavity and the choice of theposition f of the membrane or `disc transmitting the pressure tional tothe 10W frequency variations'of p.

teringa'pparatus. The form of the cavity willb chosen so asteincreasethe pressure of radiation Y increased for one same Wavelength,-at least in the` ratio '.1 to 50.

a` Wave guide, the .Equation 1 islyet applicable and, from the general.'relationsfbetween E and I-I ina.y guide for fa; determined type ofwave, it is deduced that ,the mean Vvalue of the pressure of radiationis rigorously proportional to the mean value of the iiux of energythrough a crosssection ofzthe guide; hence: n

` .l Pbaryes=KWwatts Y 4 Y y This pressure will be directly measured, orthe variations of the pressure (causedby the variation of powercirculating in the guide) will be detected throughany device sensitivetolow pressures but characterized by the fact that the elastic elementof yhigh surface conductivity on which the pressure of radiation exertsitself closely kfits the form of this wall and connects with it by a`jointof such dimensions that it forms a short-circuitfor ultra-highfrequency waves. The numerical results ,given below will constitute anapplication 'of the above formula,

P baryes :KWwatts a, thefvalue of K is:

cos

where f f l2b and I)eis thel wave length in vacuo. It appears that forasame `value of u, K is greater when A is smaller, that is to say thatrthe pressure of ra.-

diation on the walls isinoreasingly greater when the wave length becomessmaller and smaller. For A=20 c`m. and a guideof 5 l5 cm.,

and, followingjthe maximum of ythe absolute Y -valueof the mean pressure(obtained either at the middle of 'side b, or at any pointof side a) is:

Pbaryesr=24 10`5 Wwatts The devices will'be described now with more 1particulars. y Y y Fig. 5 represents the `diagram ofthe principle of thearrangement: S is a high frequency'source Y* (klystron,"magnetron)feeding to a guide of rectangular waves G; yM is the modulator used formodulating the ultra high frequency of the gen- Y erator; D is thedetector ofpressure (microphone element, piezoelectric quartz etc.)where the metallic or metallized element submitted `to pressure ispresent in thev center of the Wall of the guide; A is an amplifier and Ba meter or a loudspeaker. y l f YIn the absence of low frequencymodulation,

the `indicationof meter B gives the value-of the, i

the hole.

spasmes' pressure exerted`on'D,` and consequently -fthevaue of; the eldiat thei-wallofii the guide; following;

there is* obtained: the'ultrahighLfrequenny power circulating in. theguide. if this; one f is traversed by progressive'- wavest.' Bydisplacing. D ralong: a longitudinal sloti-provided. ini. the: axis.itself; of: the wall (which will be slotted for.' that purpose) i, the:indication of Bi remainsl unchanged; if.; in guide G; vonlyprogressivawaves': are. circulating; whereupon; eventual variationsrofl2v willsglve;- .as it is well known; they proportion of. stationary.waves: in the guide, whence.r oneuwillv deduc'ezf the eiective value" ofthe power' transmitted by fgenerator S.

If the ultra high frequencypower is modulated; the variations yofindicator B will be proportional Y to the variations of power and thedevice will be used, together with lthe knownmean's,` asa modulationcontroller. v

Fig. 6 shows anexample oflemb'odiment otlief detector of' pressurevD;it=V isy constituted;v bya microphonic capsule withalmetallizedmembrane; which= is locally substitutedr to -the wall a(perforatedrv forv that purpose)` ofi' a2. guide Gf: offv aV'rectangular section.

There will be= nowf described; byway ofi nonlimitative example, a modeoiembc'dimentlwhicli modulation as utilize chopping; whichvsystems areencountered in generators of non-linear characteristics, such as theauto-oscillating kyglstrons. or" again' for* multiplexI connections.Thisprocess is describedin Philips Technical Review, issueofOctoberl9'3'', page 301;V

The modulator M Fig. 5" is quart'zcontro-lled' and chops the powertransmitted by S into rectangular signals at afrequency of '8D kc. forinstance, the low frequency modulation being obtained by varying thewidth of the signals: The detector D is constituted by a prismaticquartz of Curie cut, resonating on the frequency of the control, that is80 kc., and the base of which, whereon the pressure of radiation isexerted, is platinized, the dimensions` ofthis base quartz is located inthe center ofthe facefbof a-.guide of a rectangularsection 4(xxliicm.traversed by a progressive wave H01 of a wave length of 20 cm., itisoundthat thefvoltage is 14 p. v.

Vper watt circulating in the guide, a value quite sufcient forapplication to an ordinary, amplifier.

Fig.. 7'shows the section of'such ad'etector: Gl is the wall ofthevguide, it is piercedlwithv a square hole .through which there isintroducedlth'e platinized base f of quartz Q in such a waythat .thesameis coplanar Withwall G. without the'A quartz coming laterally incontact withv the. rims of The metallic coatingof.I f extendsby 2 mm. onthe longitudinal'. faces.. of .'thequartz so as to form a shorty circuitfor theultra frequency. The quartz is held. by twogelectrodes, E,applied respectively toy thecenterxof 'twoopposite faces of thisquartzandfastened by pres-.- sure screws to` two feetT.- ofinsulating'material, integralwith the wall of the guide. The voltageappearing at the terminals E feeds tofamplier. Ai ill-.slidingsystem,`which-.isv-noti shown, permitsv the' detector-i to be displaced.longitua c Si dinally-falongthe pgu'ideg: su"v as: toi: measure; theproportlonrofstationary waves:

It:I is-obviou'slL that, touse the.: system?. of.: Fig. .7 as al.modulation. controller.: it will; be' necessary touchoose. thefrequencyl and' the. qualityffactor oithepiezoelectriccrystal insuchmanner that the low frequency modulation band may. passthroughisuificientlyfwelll To'ithisiend'; it-will beofadvantagetoassociate severalfdetecting quartz crystals in a knownmannerg-'to'form anhand-pass filter:

Inrthefztlreory@ developed by-Maxwell itzis established',s that; thfeiirradiation pressure'VV of electromagnetic.radiation;..is.proportional.ato the energy expressedbyfth'e,Royntingvectoi" that is" to say.'

to the square ofttheielectromagnetictfield intensit'yf: This isi:recognized?. inathei physics"I text book-lbylrof. `Die RiTomaschekgentitle'd#Grimsehls'iLeln-buehi.derrPhysike kZweiten Band,1936; atr584-59mf To? measure: the irradiation pressure. thusf the: samef thing; as', measuring terminusfrof said .cable' and:x having-t anrenclosing- Wall.poi-tion` for' re'ectin'gi'. ultrafhigh frequency: wavesinterlorly of said Wave guide-,andaL mechanical pressure:operateddetectorflocated withinlsaidlguideifamtresponsive to mechanicalpressuresrzldeveloped". by ultra high:v frequency, waves incident uponsaid wave guide;l

2:. In: an ultra' A'.hi'ghf frequency-.- measuring-systenr incombination with'facoaxial cable; an ultra' high:` frequency-"wave:guide connected. with. the

, terminusx of.I said f cablevand; having; an 1 enclosing'V wall@portion for:vr reflecting.; ultraf high frequency;r wavesinterior1y;.of:-said.:waveguide a:piezoelec' tric crystal L mountedfinfsaid. wave =guide,'.and 1an indicating circuit -connectedwithsaidpiezoelectriecrystal A.andfresponsiveato :currents -generatedbyvsaid piezoelectric crystal underA vconditionsv of pressure.A`effects:v developed.' by; ultra' high`v frequency; waveszw-ithin :saldiwavesguide.

3: Inl an` appara-tus# for,` measuringf irradiation.pressureffofrultra-short .waves on the'l insideof -aductwith .avconductiveenvelope; -infcombina-y tion, .a conductivet envelope f`having-' an opening therein, an elastic element of high surfaceconductivity insertedY with a loosetzin'said opening,

. means for exciting an ultra-high frequency electromagneticfleidfawithirn said: duct.. and?. means: associated with theusaid elasticelement-which1 transformsrthefforcesfzdueffto: saidleld: and acts onsaid element to a-measura'ble'electricimagnicavityfov the Afrequeneyjofthe uma-short" wave,

alrelay connected [with said elastic element, means for-z-tra'ns'f'rmingf-the `forces 'exerted by these Awaves, on the elementinto a measurable electric wave -for` determining the amplitude of theperiodic yariation of the strength of the wavethro'ugh'the measurementofl the amplitu'de'of this' current.

a1 piezoelectric crystal having a. metallized face y is inserted finthis hole with aloose iit so as tobe substantially coplanar with thewall, the inherent frequency'ofvibration-of the said crystal beingA asclose as possible tothe frequency of modulation of the wave, means forcollecting `between two electrodes'applied on vtwo otherparallel facesof said crystal, a current whose amplitude is at any7 time proportionalto the amplitude of the modulation of thewave. and means for amplifyingsaid current and for measuring its amplitude.

6".v In a device for propagating ultra-short waves through its interiorand which is provided with a highly conductive metal wall enclosing aresonant cavity, a coaxial feed conductor connected with said cavity forintroducing therein non-modulated waves of ultra-high frequency, anelastic element of high surface conductivity inserted with small play ina hole of corresponding form cut out in a fiat part of said wall andsubstantially coplanar with said wall, means for equalizing the inherentfundamental frequency of the cavity to the frequency of the carrier waveand for suppressing any'reection of waves in the coaxial feed conductor,a piezoelectric crystal connected with said elastic element, andmeansfor collecting electric charges on two parallel faces of said crystaland for transmitting them to an electrometer having calibrationsenabling the direct reading thereon of the constant strength of thewave.

7. In combination, a generator of non-modulated ultra-high frequencywaves, an emitter of impulse of periodically variable durations and ofka predetermined recurrence frequency for controlling the emission of thegenerator whereby the emission of said generator is modulated inaccordance with said variable impulse durations, a wave guide ofstraight rectangular section in one of whose walls there is cut out ahole of symmetrical form whose axis is parallel tojthe longitudinalVaxis of this wall, a piezoelectric crystal of the same inherent.frequency asfthe said recurrence frequency and one face and a measuringapparatus constituting a modu- .said microwave energy tov providemechanical displacement thereof substantially onlyin response toelectrostatic field stresses induced in said element by' said 'eld,employing said mechanical displacementl of 'said element'to controlelectrical eners'yand measuring said controlled electrical Energy.

510'; ,'The method oflutilizingamovable elementV for measuring microwave"energy comprising the steps of subjecting said element to theY field of"said microwave energy .to provide mechanical displacement thereofsubstantially only in responseto'electrostatic eld stresses induced insaid element'by said field, employing said mechanical displacement ofsaid element to generate electrical energy, and measuring said generatedelectrical energy.

11. The method of utilizing a movable element for detecting a microwavefield comprising the steps of subjecting said elementto said field toprovide mechanical displacementA thereof substantiallyonly in responseto electrostatic field off-@which of high surface conductivityl isinserted in this hole with small play and Abeing coplanar with the saidwall, means for collecting between twoparallel faces of the lastmentionedpiezoelectric quartz crystal a current whose amplitude is atall times proportional to the modulated strength of the wave whichcirculates in the wave mdulation band of the wave, an amplifier suit#ably-connected with the said piezoelectric crystals,

stresses induced in said element by said field, controlling electricalenergy in response to said displacement of said element, and detectingsaid controlled electrical energy.

12; The method of employing a movable element for detecting microwavetransmission through a waveguide transmission system comprising thesteps of subjecting said element substantially only tothe microwaveelectrostatic field within said waveguide to displace said element as afunction of the strength of said electrostatic field, employing saidmechanical displacement of said element to control electrical energy,and utilizing said controlled electrical energy.

13. Apparatus for measuring microwave energy comprising a conductor, `avsource of electrical energy, means for subjecting said conductorsubstantially only to the electrostatic eld of said microwave energy todisplace said conductor as a function of the strength of saidelectrostatic field, means for employingy said mechanical displacementof said conductor to control said elec* trical energy, and means formeasuring said controlled electrical energy.`

14. Apparatus for measuring microwave energy in a transmission'systemcomprising a conductive element subjected substantially only to theelectrostatic eld of said microwave energy whereby said element ismechanically displaced as a function of the strength of saidelectrostatic eld, a source of electrical energy, means for controllingsaid electrical energy source in response to said displacementof vsaidelement, and means for measuring said controlled electrical energy.

15. Apparatus for detecting a microwave electrostatic field comprising amechanical coupling,

said coupling, and means" for utilizing said controlled electricalenergy. y n

1.6, Apparatus for detecting microwave transmessage,

as a function ofthe metgnitudeof the electro- 5 static eld of saidmicrowaves,jaisonrcefielec trical energy, means `1esponsivetogfsaidfmechanical displacement -of said element for Qontrolling saidelectrical :energLand means for detecting said controlled electrical;energy. 10

17. Apparatus for detectingfmirowave :transmission through a waveguidetransmissionsystem including a yeldableoonduotive..element forming aportion of ksaid waveguide-and-subjectedsub- Kstantally only to vtheelectrostatic field Vof esaid 1 microwaves in a manner whereby saidelement is Ymechanicallyv displaced as :e rfimotion of the magnitude of-said ;;m,oriowav,e electrostatic rield,

a source of electrical genergy, means :coupled t0 12 sadzelementrandfresponsiveztosed displacement thereofgfomontrollng saide1ectr1cal;enerey, and Lmeans for -gtilizing said :controlled-electricalenergy. Y

JEAN BERNIER.

morenas onen ijn the .meer this panent UNITED STATES PATENTS Number NameDate 21299;260 'Sivian Oct.20194,2 12,402,544 Fou1ds June `25, 1,946'2),V4 02,j663 Ohl June;25, 1946 2,44% 614 YV'Norton June 1,-1'9482,453,532 `.Iforton o o- Nov. 9:1948

`FOREIGN PATENTS Number Country Date 5:48581 Greatrtain.,.., `00t- 201,942

